In order to design reliable ceramic components, it is essential to be able to predict their behavior under in-service conditions. Typically, small scale laboratory strength studies are performed on ceramic specimens under a known stress state, i.e., flexure and/or tension. The studies are performed at room temperature to establish base line strength data from which to assess the effects of other variables (e.g., temperature and environment) on the strength behavior of the ceramic material. Industrial components are often subjected in actual use to complex stress states which are unable to be simulated in the laboratory.
Size also affects the strength characteristics of ceramics, in that, with increased size, the strength of ceramic components generally decreases. This affect is attributable to the nature and distribution of intrinsic microscopic flaws that are unavoidably present as a result of material processing and/or handling. Similarly, for materials which exhibit creep or time dependent strength behavior at elevated temperatures, laboratory studies can be performed on small specimens to predict the lifetime of a component. Statistics from such studies predict the strength and reliability of the ceramic component under test. However, the inability to test full size components in service environments causes such statistics to be subject to question.
Ceramic tubes are widely used in radiant tube and heat exchanger applications. It is desirable to clarify the failure possibility of such tubes under actual operating (temperature and pressure) conditions.
Pressure testing of ceramic components is known in the prior art. Much of that prior art relates to pressure testing of glass and other ceramic types of bottles. In U.S. Pat. No. 3,785,195 to Yasuhiro (see FIGS. 5 and 6), an annular packing is caused to expand and seal the interior of a bottle's throat so that a pressure test can be accomplished. The sealing action occurs due to an upwards movement of a nozzle portion of the sealing mechanism with respect to a collar, thereby causing expansion of the annular packing. In U.S. Pat. No. 2,592,984 to Walling, another bottle pressure testing system is shown wherein (see FIG. 5) the neck of the bottle is forced against a resilient member sealer while pressure testing occurs.
Additional bottle testing systems can be found in U.S. Pat. Nos. 3,958,448 to Willis et al., 3,955,402 to Harvill, and 4,788,850 to Buschor.
Other testing systems for pressure testing vessels can be found in U.S. Pat. Nos. 3,365,933 to Jorgensen et al., 4,553,424 to Tkachuk and 3,916,673 to Gass et al. Pressure testing has also been applied to systems, e.g., see 2,685,060 to Pierce et al. (spark plugs); 2,966,791 to Ivans (explosive testing) and 3,557,606 to Markey (for gauging work piece dimensions as a work piece undergoes fluid pressure expansion). None of the above cited prior art indicates an ability to test a ceramic vessel at elevated temperature while maintaining a high pressure sealing action at vessel openings.
Accordingly, it is an object of this invention to provide an improved high pressure, high temperature test apparatus for tubular members.
It is another object of this invention to provide an improved high temperature, high pressure testing apparatus wherein pressure seals maintain their sealing action under the high temperature conditions.
It is a further object of this invention to provide a high temperature, high pressure testing apparatus for ceramic tubes wherein such tubes can be tested to failure under conditions of safety.